Field of the Disclosure
The present invention relates to a motor, more particularly, to a motor that is able to reduce the manufacture price, with an easy manufacture process and improved product reliability.
A motor according to embodiments may be a motor applied to a washing machine and examples of apparatuses the motor can be applied to are not limited to the washing machine.
Discussion of the Related Art
Generally, a motor is configured to transfer a rotational force of a rotor to a shaft for the shaft to drive a load. For example, the shaft is connected to a drum provided in a washing machine to drive the drum or it is connected to a fan provided in a refrigerator to drive the fan to supply cold air to a space requiring the cold air.
In such a motor, a rotor is rotated by an electromagnetic interrelation with a stator. For that, a coil is wound around the stator and currents are applied to the coil, to rotate the rotor with respect to the stator.
The stator includes a stator core and the stator core is formed of a conductor. The stator is typically fixed to an object. Fixing means are required to fix the stator to such an object as a motor housing or a motor bracket. In addition, the coil is wound around the stator and insulation means have to be provided between the coil and the stator core. A tap terminal structure has to be provided to apply the powder to the coil.
Because of such characteristics of the motor, the stator has to include the fixing means mentioned above, the stator core, the coil and the insulation structure for insulation from the tap terminal.
The coil is typically formed of copper. This is because copper has a good electrical conductivity and a good ductility, with less damage when it is wiring.
However, such a copper material has a high raw price enough to increase the production cost of the motor. Internationally, copper demand is rising suddenly such that stable supply and demand of copper cannot be performed frequently.
As a result, it is proposed that a coil formed of another material, not the coil formed of the copper should be used to lower the production cost of the motor and to make stable supply and demand of raw materials. In addition, even when the coil formed of another material is used, it is necessary to manufacture a motor having at least the same or better quality, compared with the conventional copper coil.
Meanwhile, in case the copper coil is replaced with the coil formed of another material, it is preferred that a conventional structure of a motor is not changed greatly. Even if the raw price of coil is reduced, the other components have to be designed and fabricated newly. In this instance, there are concerns of high design costs and initial equipment investment costs.
Referring to FIGS. 1 and 2, a conventional motor will be described in detail as follows. The motor shown in the drawings is one example of a motor for driving a drum provided in the washing machine. The motor is an outer rotor type motor having an outer rotor rotated on a stator. However, the present invention is not limited such the motor.
First of all, referring to FIG. 1, a stator composing the conventional motor for the washing machine will be described.
A stator 100 may include a stator core 110, an upper insulator 120 and a lower insulator 130.
The stator core 110 has a back yoke and teeth 112 projected in an outer radial direction along an outer circumference of the back yoke 111. FIG. 1 illustrates the stator provided in the outer rotor type motor including the rotor which will be described later. Alternatively, the teeth may be projected in an inner radial direction along the outer circumference of the back yoke 111. In this instance, the stator may be a stator provided in an inner rotor type motor.
Meanwhile, to form the stator core 110, steel sheets are blanked and layered. However, in case of using such a method, the circular steel pieces generated in the stator core cannot be used and material waste might be caused. Accordingly, it is preferred that a band-shaped back yoke and teeth projected from the back yoke perpendicularly are curved and layered in a spiral shape, to be a spiral core type. Such a spiral core is shown in FIG. 1.
A caulking 113 is formed in the layered annular back yoke 111 to make the layers coupled to each other so as to form stator core integrally.
A coil (not shown) is wound around the teeth 112. However, the teeth may generally be formed of a conductive material and an insulator is provided between the teeth and the coil to insulate the teeth from the coil. For example, insulators 120 and 130 are provided on and under the stator core 110, respectively. In other words, an upper insulator 120 and a lower insulator 130 are coupled to upper and lower portions of the stator core 110, respectively, to surround the stator core 110. At this time, the coil is wound around wiring portions 120A and 130A surrounding the teeth 112.
The wiring portions 120A and 130A may include teeth receiving portions 121 and 131. In other words, the teeth 112 may be insertedly received in the teeth receiving portions 121 and 131, such that the teeth receiving portions 121 and 131 may be positioned between the wound coil and the teeth 121 for insulation between the coil and the teeth.
Meanwhile, the insulators 120 and 130 include fixing portions 120B and 130B provided outside or inside with respect to a radial direction of the wiring portions 120A and 130B.
The wiring portions 120A and 130A and the fixing portions 120B and 130B may be integrally formed as one body. In other words, the upper insulator 120 may be configured of the wiring portion 120A and the fixing portion 120B integrally formed with each other. The insulator 120 and 130 may be formed of a plastic material and the plastic material is injected in a mold as one body.
Here, the wiring portion 120A and 130A may be the portions connected to the teeth 112. The fixing portions 120B and 130B may be the portions connected to the back yoke 111. Accordingly, the wiring portion is configured to perform an insulation function between the back yoke and the teeth and the fixing portion is configured to perform an insulation function between the back yoke and the other components. The other components may include a coil, coil ends, an object where the stator is fixed and the like.
The fixing portion 120B and 130B may include a coupling boss 125 and 135 projected in an inner radial direction. A coupling hole 126 and 136 may be formed in the coupling boss to fixedly position the stator to a rear wall surface (not shown) of a tub provided in the washing machine. Such a coupling boss is not necessarily configured to fix the stator to the tub. According to embodiments, the coupling bosses 125 and 135 may be configured to couple the stator to a bracket (not shown) or a motor housing (not shown) defining an exterior appearance of the motor.
In case the washing machine is a horizontal shaft type, the stator 100 is fixed to a rear wall surface of the tub and to drive the drum directly. In case the washing machine is a vertical shaft type, the stator is oriented to a lower wall of the tub to drive the drum directly. An upper part of the vertical shaft type washing machine can be a front surface and a lower part thereof can be a rear surface. Accordingly, in any types, the stator 100 can be fixed to the rear wall surface of the tub.
The coupling hole 126 of the upper insulator and the coupling hole 136 of the lower insulator are corresponding to each other to form one coupling hole 126 and 136, when the upper insulator, the stator core and the lower insulator are coupled. The entire stator may be fixed to the tub mentioned above by fastening a bolt (not shown) to the coupling hole.
Moreover, a position determination projection 127 may be formed adjacent to the coupling hole 126 of the upper insulator. Specifically, the position determination projection is inserted in a groove (not shown) formed in the tub and the position of the stator 100 is determined. After that, the stator 100 can be secured by using the bolt mentioned above.
Meanwhile, the coil corresponding to u, v and w power phase may be wound around the stator shown in FIG. 1. One coil may be wound around one tooth to make one tooth have one magnetic pole, which is called as “concentrated winding”. As there are more and more magnetic poles, the maximum rotational number of the rotor is getting lower. Accordingly, it can be easier to control the motor and the highest torque can be relatively increased.
First of all, the winding of the coil around one tooth on the u angle is completed, the coil is fixedly wound around a coil winding rib 122 formed in the upper insulator and then wound around the next tooth, after passing two neighboring teeth. A starting end and the finishing end of the u-coil is positioned at a tap terminal 128 for power connection and a neutral point tap terminal 129, respectively. Coils are wound on v and w power phase according to such a method.
Here, a connector 140 is connected to the tap terminal for the power connection and a 3-phased power is applied to the coils on u, v and w power phase. Also, ends of each coil are electrically connected with each other at the neutral point tap terminal 129 to form the neutral point.
Outer surfaces of the tap terminals 128 and 129 are formed of an insulative material, integrally formed with the insulator. In other words, the fixing portion 120B of the insulator may include the tap terminals 128 and 129. Accordingly, when coil ends are fixedly positioned at the tap terminal, the insulation may be performed between the stator core and the coil ends.
Meanwhile, a hall sensor assembly 141 is fixed in the tap terminal, in other words, the tap terminal 128 for power connection and the neutral point tap terminal. The position and/or speed of the rotor may be sensed via the hall sensor assembly, to adjust the phase of the applied voltages and the intensity of the currents so as to control the rotational number and torque of the rotor.
An insulator rib 123 may be formed in an inner radial portion of the coil winding rib 122 in a circumferential direction. Such the insulator rib 123 is formed not only in the upper insulator but also the lower insulator. The insulator rib 123 has a predetermined height or more to perform a function of blocking the moisture of the insulator from flowing to the wiring portions 121 and 131.
In addition, it is preferred that the height of the insulator rib 123 is larger than the height of the wound coil. This is because there is concern of damage to the coil caused by other objects placed nearby when the stator 100 is treated. In other words, when placing the stator on the floor, only the insulator rib 123 is in contact with the floor and the coil is not in contact such that the coil damage can be prevented effectively.
Also, the insulator rib 123 may be configured to distinguish the portion where the coil ends are fixed or the coil is wound or moved in the insulator from the portion where the stator is fixed to the object. Accordingly, electric leakage of currents flowing to the object via the coil can be prevented.
Referring to FIG. 2, the rotor provided in the motor for the conventional washing machine will be described.
The rotor 200 provided in the conventional motor includes a rotor frame 210 and a permanent magnet 216.
The rotor frame 210 includes a base 212 and a lateral wall part 211 coupled to lateral portions of the base. The base 212 and the lateral wall part can be formed by pressing one steel plate. Here, a plurality of permanent magnets can be provided in inner portions of the lateral wall part along a circumferential direction. The permanent magnets are alternated in an order of N and S poles.
The lateral wall part 211 is functioned as a back yoke for forming a magnetic circuit.
Alternatively, the rotor frame can be formed according to an injection molding process and an annular magnetic back yoke can be additionally provided in this instance.
A raised hub 213 is formed in a central portion of the base 212 to reinforce the rigidity of the base. The hub 213 has a penetrating hole 219 formed in a central portion and a shaft (not shown), for example, the shaft of the washing machine is positioned in the penetrating hole. The shaft and the hub 213 can be connected with each other via a connector not shown in the drawings such that the rotational force of the rotor can be transmitted to the shaft as the rotor is rotated.
The coupling hole 214 configured to couple the connector therein or the position determination groove 215 configured to determine the coupling position of the connector may be formed in the hub 213.
Such the rotor 200 receives the stator 100 therein and it is rotated with respect to the stator 100 according to the interrelation with the stator. The rotational force of the rotor is transferred to the shaft (not shown) integrally rotated with the rotor frame 210.
In the conventional motor mentioned above, the insulator 120 and 130 includes the fixing portion 120B and 130B and the winding portion 120A and 130A. In other words, the winding portion extended from an inner or outer radial portion along a radial direction of the fixing portion. Accordingly, the insulator is configured to be coupled to the back yoke 111 and the teeth 112 as an independent element.
The number of the winding portions is increasing according to the number of the teeth formed in the stator 100. Like the teeth, the winding portions may be spaced apart from each other along a circumferential direction. The appearance of the insulator having the fixing portions and the winding portions integrally formed with each other might be so complicated that it is not easy to fabricate such the insulator.
Moreover, when fabricating or treating the insulator, the winding portions are likely to have damage. It is limited to enhance the rigidity of the portion where the winding portions 120A and 130A are connected to the fixing portions 120B and 130B and it is closely related to the thickness and material of the winding portions.
As the thicknesses of the winding portions are increased, the gap between the winding portions is getting narrower. This is because the thickness of the winding portions covering both lateral surfaces of the teeth is increasing. The frequency of winding the coil around the winding portions cannot help decreasing noticeably, because the minimum insulation distance has to be secured between each two neighboring coils.
As the thicknesses of the winding portions are increasing, the height of the coil cannot help increasing noticeably. This is because the thickness of the winding portion covering the top or lower surfaces of the teeth is increasing. Accordingly, the height of the wound coil cannot help increasing remarkably. There might be a problem of unnecessarily increased stator volume and another problem of unnecessarily long length of the coil.
Those problems will be explained easily as follows. The frequency of winding the coil and the cross section area of the teeth 112 are important. As mentioned above, the coil is wound around the teeth 112. When the cross section area of the teeth 112 is determined, the winding frequency and height of the coil and the overall length of the coil can be uniform. However, as the plastic structure surrounds the teeth 112 as mentioned above, the coil is wound around the plastic structure and the cross section area where the coil is substantially wound is remarkably increase. Such increase of the cross sectional area can increase the height and the overall length of the coil noticeably. Moreover, it is limited to increase the coil winding frequency.
More specifically, a horizontal portion of the coil wound around the winding portion is irrelevant to the performance of the motor, except a vertical portion of the coil. The increase of the horizontal length of the coil results in increasing the material cost and weight of the motor as well as the resistance of the coil, such that ohmic loss could increase. This can be directly connected with deterioration of motor efficiency.
Accordingly, demands for a motor having an easy fabrication process and a reduced failure rate are increasing. There is a growing need to provide a motor having an enhanced efficiency and a reduced material cost.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.